Abstract
Electric vehicles (or hybrid ones) are very silent at low speeds (below 30 km/h) and can be dangerous for pedestrian, especially vulnerable ones as visually impaired people. The European founded project eVADER aims at developing a prototype vehicle including an automatic pedestrian detection device and an array of speakers focusing a warning sound in the direction of the pedestrian. The warning sound should be optimized too, in order to be easily detectable while not too loud. Research is conducted in order to investigate the influence of some timbre parameters on the detectability and annoyance of warning sounds.
Different warning sounds were synthesized according to a fractional factorial design. Factors were related to three basic timbre parameters. Two laboratory experiments took place. The first one focused on detectability. The task of the listener was to detect an approaching car (20 km/h) as soon as possible. The second experiment was devoted to the unpleasantness of warning sounds. Stimuli were presented to listeners who had to evaluate their unpleasantness on a continuous scale.
The tests have shown that some warning sounds can make an electric vehicle as detectable as a diesel car, for a much lower sound level. However, most warning sounds also tend to increase the unpleasantness of the car sound. Nevertheless, some signals seem to provide a good compromise between the two objectives.
KEYWORDS – Electric and Hybrid Vehicles; Warning Sounds; Pedestrian Safety